Image displaying device and method

ABSTRACT

It is an object to prevent the image quality deterioration of a moving image likely to include a plurality of the same consecutive images such as a movie video image or a CG video image due to the motion-compensated frame rate conversion (FRC) processing. An image displaying device is provided with an FRC portion ( 10 ) for converting the number of frames in an input image signal by interpolating an image signal to which a motion compensation processing has been given between the frames in the input image signal, a controlling portion ( 14 ) for controlling each portion according to an image tone mode selected by a user. The FRC portion ( 10 ) includes a motion vector detecting portion ( 11   e ) for detecting a motion vector between the frames of the input image signal, an interpolating vector evaluating portion ( 11   f ) for allocating an interpolating vector between the frames based on the motion vector information, and an interpolating frame generating portion ( 12   d ) for generating an interpolating frame from the interpolating vector. In the case that the image tone mode selected by the user is a predetermined image tone mode, the controlling portion ( 14 ) set the motion vector detected by the motion vector detecting portion ( 11   e ) to zero-vector to make the motion compensation processing of the FRC portion ( 10 ) ineffective.

TECHNICAL FIELD

The present invention relates to an image displaying device and methodhaving a function of converting a frame rate or field rate, and moreparticularly, to an image displaying device and an image displayingmethod of the device, which include preventing the image qualitydeterioration of a moving image likely to include a plurality of thesame consecutive images due to a motion-compensated rate conversionprocessing.

BACKGROUND OF THE INVENTION

As compared to conventional cathode-ray tubes (CRTs) primarily used forrealizing moving images, LCDs (Liquid Crystal Displays) have a drawback,so-called motion blur, which is the blurring of outline of a movingportion perceived by a viewer when displaying a moving image. It ispointed out that this motion blur arises from the LCD display modeitself (see, e.g., Specification of Japanese Patent No. 3295437;“Ishiguro Hidekazu and Kurita Taiichiro, “Consideration on MotionPicture Quality of the Hold Type Display with an octuple-rate CRT”,IEICE Technical Report, Institute of Electronics, Information andCommunication Engineers, EID96-4 (1996-06), p. 19-26”).

Since fluorescent material is scanned by an electron beam to causeemission of light for display in CRTs, the light emission of pixels isbasically impulse-like although slight afterglow of the fluorescentmaterial exists. This is called an impulse display mode. On the otherhand, in the case of LCDs, an electric charge is accumulated by applyingan electric field to liquid crystal and is retained at a relatively highrate until the next time the electric field is applied. Especially, inthe case of the TFT mode, since a TFT switch is provided for each dotcomposing a pixel and each pixel normally has an auxiliary capacity, theability to retain the accumulated charge is extremely high. Therefore,the light emission is continued until the pixels are rewritten by theapplication of the electric field based on the image information of thenext frame or field (hereinafter, represented by the frame). This iscalled a hold display mode.

Since the impulse response of the image displaying light has a temporalspread in the above hold display mode, spatial frequency characteristicsdeteriorate along with temporal frequency characteristics, resulting inthe motion blur. Since the human eye can smoothly follow a movingobject, if the light emission time is long as in the case of the holdtype, the movement of image seems jerky and unnatural due to the timeintegration effect.

To improve the motion blur in the above hold display mode, a frame rate(number of frames) is converted by interpolating an image between framesin a known technology. This technology is called FRC (Frame RateConverter) and is put to practical use in liquid crystal displayingdevices, etc.

Conventionally known methods of converting the frame rate includevarious techniques such as simply repeating read-out of the same framefor a plurality of times and frame interpolation using linearinterpolation between frames (see, e.g., Yamauchi Tatsuro, “TV StandardsConversion”, Journal of the Institute of Television Engineers of Japan,Vol. 45, No. 12, pp. 1534-1543 (1991)). However, in the case of theframe interpolation processing using the linear interpolation,unnaturalness of motion (jerkiness, judder) is generated due to theframe rate conversion, and the motion blur disturbance due to the abovehold display mode cannot sufficiently be improved, resulting ininadequate image quality.

To eliminate effects of the jerkiness, etc., and improve quality ofmoving images, a motion-compensated frame interpolation processing usingmotion vectors is proposed. Since a moving image itself is captured tocompensate the image movement in this processing, highly natural movingimages may be acquired without deteriorating the resolution andgenerating the jerkiness. Since interpolation image signals aregenerated with motion compensation, the motion blur disturbance due tothe above hold display mode may sufficiently be improved.

Above Specification of Japanese Patent No. 3295437 discloses atechnology of motion-adaptively generating interpolating frames toincrease a frame frequency of a display image for improvingdeterioration of spatial frequency characteristics causing the motionblur. In this case, at least one interpolation image signal interpolatedbetween frames of a display image is motion-adaptively generated fromthe previous and subsequent frames, and the generated interpolationimage signals are interpolated between the frames and are sequentiallydisplayed.

FIG. 1 is a block diagram of a schematic configuration of an FRC drivedisplay circuit in a conventional liquid crystal displaying device and,in FIG. 1, the FRC drive display circuit includes an FRC portion 100that converts the number of frames of the input image signal byinterpolating the image signals to which the motion compensationprocessing has been given between frames of the input video signal, anactive-matrix liquid crystal display panel 104 having a liquid crystallayer and an electrode for applying the scan signal and the data signalto the liquid crystal layer, and an electrode driving portion 103 fordriving a scan electrode and a data electrode of the liquid crystaldisplay panel 104 based on the image signal subjected to the frame rateconversion by the FRC portion 100.

The FRC portion 100 includes a motion vector detecting portion 101 thatdetects motion vector information from the input image signal and aninterpolating frame generating portion 102 that generates interpolatingframes based on the motion vector information acquired by the motionvector detecting portion 101.

In the above configuration, for example, the motion vector detectingportion 101 may obtain the motion vector information with the use of ablock matching method and a gradient method described later or if themotion vector information is included in the input image signal in someform, this information may be utilized. For example, the image datacompression-encoded with the use of the MPEG format includes motionvector information of a moving image calculated at the time of encoding,and this motion vector information may be acquired.

FIG. 2 is a diagram for explaining a frame rate conversion processing bythe conventional FRC drive display circuit shown in FIG. 1. The FRCportion 100 generates interpolating frames (gray-colored images in FIG.2) between frames with the motion compensation using the motion vectorinformation output from the motion vector detecting portion 101 andsequentially outputs the generated interpolation signals along with theinput frame signals to perform processing of converting the frame rateof the input image signal from 60 frames per second (60 Hz) to 120frames per second (120 Hz).

FIG. 3 is a diagram for explaining an interpolating frame generationprocessing of the motion vector detecting portion 101 and theinterpolating frame generating portion 102. The motion vector detectingportion 101 uses the gradient method to detect a motion vector 105 from,for example, a frame #1 and a frame #2 shown in FIG. 3. The motionvector detecting portion 101 obtains the motion vector 105 by measuringa direction and an amount of movement in 1/60 second between the frame#1 and the frame #2. The interpolating frame generating portion 102 thenuses the obtained motion vector 105 to allocate an interpolating vector106 between the frame #1 and the frame #2. An interpolating frame 107 isgenerated by moving an object (in this case, an automobile) from aposition of the frame #1 to a position after 1/120 second based on theinterpolating vector 106.

By performing the motion-compensated frame interpolation processing withthe use of the motion vector information to increase a display framefrequency in this way, the display state of the LCD (the hold displaymode) can be made closer to the display state of the CRT (the impulsedisplay mode) and the image quality deterioration can be improved whichis due to the motion blur generated when displaying a moving image.

In the motion-compensated frame interpolation processing, it isessential to detect the motion vectors for performing the motioncompensation. For example, the block matching method and the gradientmethod are proposed as representative techniques for the motion vectordetection. In these methods, the motion vector is detected for eachpixel or small block between two consecutive frames and this motionvector is used to interpolate each pixel or small block of theinterpolating frame between two frames. An image at an arbitraryposition between two frames is interpolated at an accurately compensatedposition to convert the number of frames.

Since the frames are highly correlated in moving images and hascontinuity in the time axis direction, a pixel or a small block movingin one frame tends to move with the same movement amount in thesubsequent frame or the previous frame. For example, in the case of amoving image of a ball rolling from the right to the left of a screen,the ball area moves with similar movement amounts in every frame.Consecutive frames tend to have the continuity of motion vectors.

Therefore, the motion vector in the next frame may more easily or moreaccurately be detected by reference to a motion vector detection resultof preceding frames. For example, in the iterative gradient method,which is an improved gradient method, a motion vector of a neighboringblock already detected in the previous frame or the current frame isdefined as an initial deflection vector, which is used as a startingpoint to repeat calculations of the gradient method for a detectedblock. With this method, a substantially accurate movement amount can beacquired by repeating the gradient method about two times.

A motion vector may also efficiently be detected in the block matchingmethod in such a way that a reference is made to the motion vectordetection result of the previous frame to change the search order. Whendetecting a motion vector, for example, the frame rate conversion may beprocessed in real time by utilizing the motion vector already detected.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Video signals may be sourced from videos from movie films and videosfrom computer graphics (CG) in addition to videos shot by normaltelevision video cameras. Therefore, television broadcast signals andvideo disc reproduction signals in the NTSC mode or the PAL mode ofteninclude video signals from movie films or CG. Due to the recentdevelopment in storage capacity of recording medium (e.g., DVD (digitalversatile disc), HD (hard disc)) and the digitization of transmissionmethods, video signals from various sources may be mixed.

For example, a normal movie film has 24 frames per second and, when thisfilm is output to a display having a frame rate of 60 Hz, the videohaving a frame rate of 24 Hz is to which the 2-3 pull-down processinghas been given and is converted into and output as video signals havinga frame rate of 60 Hz by outputting the same images for every two orthree frames.

When a filmed movie having 30 frames per second, or animation or a gamevideo image that is produced using CG is output on a display whose framerate is 60 Hz, the video image whose frame rate is 30 Hz is2-2-pull-down-processed and the same image is output for every twoframes and, thereby, the video image is converted into and output as avideo image signal whose frame rate is 60 Hz. When a filmed movie having24 frames per second is output on a display whose frame rate is 50 Hz,the video image whose frame rage is 24 Hz is 2-2-pull-down-processed andthe same image is output for every two frames.

As above, the original images of many filmed movies, many pieces ofanimation, and many game video images that are produced using CG, have aframe rate of 60 Hz or lower and they are output to display as a videoimage signal at 60 Hz by consecutively outputting a plurality of sameimages.

The case of a film movie having 24 frames per second described abovewill be described with reference to FIG. 4. Frame #1 to #10 of FIG. 4represents an image sequence converted into 60 Hz from a 24-Hz movievideo through the 2-3 pull-down processing. The frames #1 and #2, theframes #3 to #5, the frames #6 and #7, and the frames #8 to #10 are thesame images, respectively.

In a video likely to include a plurality of the same output images, thecontinuity of motion vectors becomes impaired between frames. Forexample, it is assumed that some kind of a moving object is shot in thevideo of FIG. 4. Although a motion vector is detected between the frames#5 and #6 since these frames are different images, a motion vector to bedetected should completely be zero between the next frames 1#6 and #7since these frames are the same images. Since the next frames #7 and #8are different images, a motion vector is detected between these frames.

With regard to the motion vectors of the successive frames from theframe #5 to the frame #7 of FIG. 4, no continuity of the motion vectorsexists between adjacent frames since “motion vector exists”, “motionvector is zero”, and “motion vector exists” are mixed in this order.

If the processing for detecting the motion vector in the next frame isexecuted by referring to the motion vector detection result of theprevious frame as above for such a video likely to include a pluralityof the same output images, it is problematic that the motion vector iserroneously detected since no continuity of the motion vector existsbetween the frames.

In the above example, although a motion vector to be detected shouldcompletely be zero between the frames #6 and #7 since these frames arethe same images, a motion vector between the previous frames #5 and #6is not zero and, therefore, a vector other than zero may erroneously bedetected by referring to this vector.

Although a motion vector should be detected between the frames #7 and #8since these frames are different images, a motion vector between theprevious frames #6 and #7 is zero and, therefore, a zero vector mayerroneously be detected by referring to this vector. It is problematicthat such an erroneous detection of the motion vector may cause theimage quality deterioration in the displayed video.

In the above type of image displaying device, a plurality of image tonesthat a user is able to select are usually equipped to designate andadjust the image quality of a displayed image corresponding to theviewing environment and the video image software. For example, a“standard mode” that sets a standard image that is definite, a “dynamicmode” that adjusts an image to be clear and to have strong contrast, a“movie (cinema/theater) mode” that adjusts a dark image to be a viewableimage by weakening the sense of contrast for video images such as amovie, and a “game mode” that adjusts an image of a video game, etc., tobe an eye-friendly image by suppressing the luminance are generally set.

Adjustment values for the luminance, the gray scale, the black level,the color thickness, the hue, the contour emphasis etc., of a screen arestored in advance corresponding to each of the above image tone modesand, thereby, the user selects a desired image tone mode. Thereby, easyand quick execution of an appropriate image quality adjustmentcorresponding to the viewing environment and the video image software isenabled. For example, when a movie program or movie software is viewed,the user is able to execute the image quality adjustment suitable forviewing a movie by selecting the “movie (cinema/theater) mode”.

Therefore, in the case where an image tone mode such as the “movie(cinema/theater) mode” or the “game mode” is selected by the user, sincea moving image that may include sections having the plurality ofconsecutive same images such as a movie video image or a CG video imageis input, it is highly probable that degradation of the image quality ofthe display video image is caused by the above reason.

The present invention was conceived in view of the above problems and itis therefore the object of the present invention to provide an imagedisplaying device and method capable of preventing the image qualitydeterioration of a moving image likely to include a plurality of thesame consecutive images such as a movie video and a game (CG) video dueto the motion-compensated frame rate conversion (FRC) processing.

Means for Solving the Problems

A first invention of the present application is an image displayingdevice having a rate converting portion that converts the number offrames or fields of an input image signal by interpolating aninterpolation image signal between frames or fields of the input imagesignal, wherein a mode setting portion for a user to select and set animage tone mode to set and adjust the image quality of a display imagefrom a plurality of image tone modes prepared in advance, wherein therate converting portion comprises an interpolation image generatingportion that generates an interpolation image signal by giving themotion compensation processing to the input image signal based on motionvector information between the frames or fields of the input imagesignal, and the interpolation of the image signal generated by givingthe motion compensation processing is not executed when the image tonemode set by the mode setting portion is a predetermined image tone modeset in advance as an image tone mode suitable for displaying a videoimage including a moving image likely to include the same consecutiveimages in a plurality of frames or fields.

A second invention of the present application is the image displayingdevice, wherein the rate converting portion interpolates an image signalgenerated by making the motion compensation processing in theinterpolation image generating portion ineffective between the frames orfields of the input image signal when the image tone mode set by themode setting portion is the predetermined image tone mode.

A third invention of the present application is the image displayingdevice, wherein the interpolation image generating portion comprises: amotion vector detecting portion that detects the motion vectorinformation between consecutive frames or fields included in the inputimage signal; and an interpolating vector allocating portion thatallocates an interpolating vector between the frames or fields based onthe detected motion vector information.

A fourth invention of the present application is the image displayingdevice, wherein the interpolation image generating portion makes themotion compensation processing ineffective by setting the motion vectordetected by the motion vector detecting portion to zero-vector when theimage tone mode set by the mode setting portion is the predeterminedimage tone mode.

A fifth invention of the present application is the image displayingdevice, wherein the interpolation image generating portion makes themotion compensation processing ineffective by setting the interpolatingvector allocated by the interpolating vector allocating portion tozero-vector when the image tone mode set by the mode setting portion isthe predetermined image tone mode.

A sixth invention of the present application is the image displayingdevice, which does not insert the interpolation image signal generatedby giving the motion compensation processing between the frames orfields of the input image signal and does not convert the number offrames or fields of the input image signal when the image tone mode setby the mode setting portion is the predetermined image tone mode.

A seventh invention of the present application is the image displayingdevice, wherein a driving frequency of a display panel displaying theimage signal is variable, and the image displaying device comprises aportion for varying the driving frequency of the display panel from theframe frequency or the field frequency converted by the rate convertingportion to the frame frequency or the field frequency of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.

An eighth invention of the present application is the image displayingdevice, wherein the rate converting portion converts the number offrames or fields of the input image signal by inserting an image signalto which the motion compensation processing has not been given betweenthe frames or fields of the input image signal when the image tone modeset by the mode setting portion is the predetermined image tone mode.

A ninth invention of the present application is the image displayingdevice, wherein the rate converting portion converts the number offrames or fields of the input image signal by inserting an image signalof the frames or fields between frames or fields of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.

A tenth invention of the present application is the image displayingdevice, wherein the rate converting portion converts the number offrames or fields of the input image signal by interpolating an imagesignal formed by giving a linear interpolation processing to an imagesignal of the frames or fields between frames or fields of the inputimage signal when the image tone mode set by the mode setting portion isthe predetermined image tone mode.

An eleventh invention of the present application is the image displayingdevice, wherein the rate converting portion converts the number offrames or fields of the input image signal by inserting a predeterminedmonochromatic image signal between frames or fields of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.

A twelfth invention of the present application is the image displayingdevice, wherein the predetermined image tone mode is movie mode.

A thirteenth invention of the present application is the imagedisplaying device, wherein the predetermined image tone mode is gamemode.

A fourteenth invention of the present application is an image displayingdevice, wherein the rate converting portion converts a frame frequencyor field frequency of the input image signal into integral multiples ofeach.

A fifteenth invention of the present application is an image displayingmethod having a rate converting process for converting the number offrames or fields of an input image signal by interpolating aninterpolation image signal between frames or fields of the input imagesignal, wherein the process in which a user is caused to select and setan image tone mode to set and adjust the image quality of a displayimage from a plurality of image tone modes prepared in advance isincluded, and the rate converting process has an interpolation imagegenerating process for generating an interpolation image signal bygiving the motion compensation processing to the input image signalbased on motion vector information between frames or fields of the inputimage signal, and the interpolation of the image signal generated bygiving the motion compensation processing is not executed when the imagetone mode set by the user is a predetermined image tone mode set inadvance as an image tone mode suitable for displaying a video imageincluding a moving image likely to include the same consecutive imagesin a plurality of frames or fields.

A sixteenth invention of the present application is the image displayingmethod, wherein in the rate converting process, the image signalgenerated by making the motion compensation processing in theinterpolation image generating portion ineffective is interpolatedbetween the frames or fields of the input image signal when the imagetone mode set by the mode setting portion is the predetermined imagetone mode.

A seventeenth invention of the present application is the imagedisplaying method, wherein the interpolation image signal generated bygiving the motion compensation processing is not inserted between theframes or fields of the input image signal and the number of frames orfields of the input image signal is not converted when the image tonemode set by the user is the predetermined image tone mode.

An eighteenth invention of the present application is the imagedisplaying method, wherein in the rate converting process, the number offrames or fields of the input image signal is converted by inserting animage signal of the frames or fields between frames or fields of theinput image signal when the image tone mode set by the user is thepredetermined image tone mode.

A nineteenth invention of the present application is the imagedisplaying method, wherein in the rate converting process, the number offrames or fields of the input image signal is converted by interpolatingan image signal formed by giving a linear interpolation processing tothe image signal of the frames or fields between frames or fields of theinput image signal when the image tone mode set by the user is thepredetermined image tone mode.

A twentieth invention of the present application is the image displayingmethod, wherein in the rate converting process, the number of frames orfields of the input image signal is converted by inserting apredetermined monochromatic image signal between the frames or fields ofthe input image signal when the image tone mode set by the user is thepredetermined image tone mode.

A twenty-first invention of the present application is an imagedisplaying device having a rate converting portion that converts thenumber of frames or fields of an input image signal by interpolating aninterpolation image signal between frames or fields of the input imagesignal, wherein a mode setting portion for a user to select and set animage tone mode to set and adjust the image quality of a display imagefrom a plurality of image tone modes prepared in advance, wherein therate converting portion comprises an interpolation image generatingportion that generates an interpolation image signal by giving themotion compensation processing to the input image signal based on motionvector information between the frames or fields of the input imagesignal, and interpolates an interpolation image signal generated byreducing the strength of the compensation of the motion compensationprocessing between frames or fields of the input image signal when theimage tone mode set by the mode setting portion is a predetermined imagetone mode suitable for displaying a video image including a moving imagelikely to include the same consecutive images in a plurality of framesor fields.

A twenty-second invention of the present application is the imagedisplaying device, wherein the interpolation image generating portiongenerates an interpolation image signal by performing weighted additionof the image signal to which the motion compensation processing has beengiven and an image signal to which the motion compensation processinghas not been given at a predetermined rate, and the rate of the weightedaddition is varied when the genre determined by the determining portionis the predetermined genre.

A twenty-third invention of the present application is the imagedisplaying device, wherein the interpolation image generating portiondefines the image signal to which the motion compensation processing hasnot been given as the interpolation image signal when the image tonemode set by the mode setting portion is the predetermined image tonemode, and defines the image signal to which the motion compensationprocessing has been given as the interpolation image signal when theimage tone mode set by the mode setting portion is not the predeterminedimage tone mode.

A twenty-fourth invention of the present application is the imagedisplaying device, wherein the interpolation image generating portionuses an image signal to which a linear interpolation processing has beengiven between the frames or fields of the input image signal as theimage signal to which the motion compensation processing has not beengiven.

A twenty-fifth invention of the present application is the imagedisplaying device, wherein the predetermined image tone mode is moviemode.

A twenty-sixth invention of the present application is the imagedisplaying device, wherein the predetermined image tone mode is gamemode.

A twenty-seventh invention of the present application is an imagedisplaying method having a rate converting process for converting thenumber of frames or fields of an input image signal by interpolating aninterpolation image signal between frames or fields of the input imagesignal, wherein the process in which a user is caused to select and setan image tone mode to set and adjust the image quality of a displayimage from a plurality of image tone modes prepared in advance isincluded, and the rate converting process has an interpolation imagegenerating process for generating an interpolation image signal bygiving the motion compensation processing to the input image signalbased on motion vector information between frames or fields of the inputimage signal, and the interpolation image signal generated by reducingthe strength of the compensation of the motion compensation processingis interpolated between the frames or fields of the input image signalwhen the image tone mode set by the user is a predetermined image tonemode set in advance as an image tone mode suitable for displaying avideo image including a moving image likely to include the sameconsecutive images in a plurality of frames or fields.

EFFECTS OF THE INVENTION

According to the present invention, the image quality determination ofdisplayed images may effectively be prevented by not executing theinterpolation processing through motion compensation when apredetermined image tone mode determined in advance (such as the moviemode or the game mode) of a plurality of image tone modes set in theimage displaying device is selected by a user.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a schematic configuration of an FRC-drivendisplay circuit in a conventional liquid crystal displaying device.

FIG. 2 is a diagram for explaining a frame rate conversion processing bythe conventional FRC drive display circuit shown in FIG. 1.

FIG. 3 is a diagram for explaining an interpolating frame generationprocessing of a motion vector detecting portion and an interpolatingframe generating portion.

FIG. 4 is a diagram for explaining an image sequence when a 24-Hz filmedmovie is converted by the 2-3-pull-down processing into a 60-Hz.

FIG. 5 is a block diagram of an exemplary configuration of a frame rateconverting portion included in an image displaying device of the presentinvention.

FIG. 6 is a diagram for explaining an example of an interpolating framegeneration processing of a frame generating portion.

FIG. 7 is a block diagram of an exemplary main configuration of a liquidcrystal displaying device according to a first embodiment of the presentinvention.

FIG. 8 is a diagram for explaining the order of selecting and switchingimage tone modes of the liquid crystal displaying device according tothe first embodiment of the present invention.

FIG. 9 is a block diagram of an exemplary main configuration of a liquidcrystal displaying device according to a second embodiment of thepresent invention.

FIG. 10 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to a third embodiment of thepresent invention.

FIG. 11 is a diagram of a relationship between input data and outputdata according to the third embodiment of the present invention.

FIG. 12 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to a fourth embodiment of thepresent invention.

FIG. 13 is a diagram of a relationship between input data and outputdata according to the fourth embodiment of the present invention.

FIG. 14 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to a fifth embodiment of thepresent invention.

FIG. 15 is a diagram of a relationship between input data and outputdata according to the fifth embodiment of the present invention.

FIG. 16 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to a sixth embodiment of thepresent invention.

FIG. 17 is a diagram of a relationship between input data and outputdata according to the sixth embodiment of the present invention.

FIG. 18 is a block diagram of an exemplary main configuration of an FRCportion according to a seventh embodiment of the present invention.

FIG. 19 is a flowchart for explaining an example of an image displayingmethod by the image displaying device of the present invention.

FIG. 20 is a flowchart for explaining another example of the imagedisplaying method by the image displaying device of the presentinvention.

FIG. 21 is a flowchart for explaining another example of the imagedisplaying method by the image displaying device of the presentinvention.

EXPLANATIONS OF REFERENCE NUMERALS

10, 100 . . . frame rate converting (FRC) portion, 11 . . . vectordetecting portion, 11 a . . . luminance signal extracting portion, 11 b. . . preprocessing filter, 11 c . . . motion detection frame memory, 11d . . . initial vector memory, 11 e, 101 . . . motion vector detectingportion, 11 f . . . interpolating vector evaluating portion, 12 . . .frame generating portion, 12 a . . . interpolating frame memory, 12 b,102 . . . interpolating frame generating portion, 12 c . . . time baseconversion frame memory, 12 d . . . time base converting portion, 12 e .. . compensation intensity varying portion, 13 . . . remote controllight receiving portion, 14 . . . controlling portion, 15 . . . imagequality adjusting portion, 16 . . . switching portion, 17 . . . zerovector, 18, 103 . . . electrode driving portion, 19, 104 . . . liquidcrystal display panel, 20 . . . path, 21 . . . memory, 22 . . . linearinterpolation processing portion, 23 . . . black level signal insertionprocessing portion, 105 . . . motion vector, 106 . . . interpolatingvector, 107 . . . interpolating frame

PREFERRED EMBODIMENT OF THE INVENTION

A preferred embodiment of an image displaying device of the presentinvention will now be described referring to the accompanying drawings.Although the present invention is applicable to either field signals andinterpolation field signals or frame signals and interpolating framesignals, the frame signals and the interpolating frame signals will bedescribed as a representative example since both (field and frame) arein a similar relationship with each other.

FIG. 5 is a block diagram of an exemplary configuration of a motioncompensated frame rate converting portion included in the imagedisplaying device of the present invention, in FIG. 5, reference numeral10 denotes a frame rate converting portion (hereinafter, FRC portion),and the FRC portion 10 corresponds to a rate converting portion of thepresent invention and is comprised of a vector detecting portion 11 thatdetects a motion vector between two consecutive frames included in aninput image signal and a frame generating portion 12 that generates aninterpolating frame (interpolation image) based on the detected motionvector. Although the iterative gradient method is used for the motionvector detection in the description of the vector detecting portion 11,the method is not limited to the iterative gradient method and may bethe block matching method.

A feature of the iterative gradient method is that several types ofmovement amounts may be detected, and a motion vector may be detectedeven from a moving object having a small region since a motion vectormay be detected for each block. The circuit configuration thereof may berealized in a smaller scale than other modes (such as the block matchingmethod). In the iterative gradient method, an already detected motionvector of a neighboring block is defined as an initial deflectionvector, which is used as a starting point to repeat calculations of thegradient method for a detected block. With this method, a substantiallyaccurate movement amount may be acquired by repeating the gradientmethod about two times.

In FIG. 5, the vector detecting portion 11 includes a luminance signalextracting portion 11 a that extracts a luminance signal (Y signal) froman input image signal (RGB signal), a preprocessing filter 11 b thatlimits a high bandwidth by applying LPF to the extracted Y signal, amotion detection frame memory 11 c, an initial vector memory 11 d thataccumulates initial vector candidates, a motion vector detecting portion11 e that detects motion vectors between frames with the use of theiterative gradient method, and an interpolating vector evaluatingportion 11 f that allocates an interpolating vector between the framesbased on the detected motion vectors.

The FRC portion 10 corresponds to the rate converting portion of thepresent invention; the motion vector detecting portion 11 e correspondsto a motion vector detecting portion of the present invention; and theinterpolating vector evaluating portion 11 f corresponds to aninterpolating vector allocating portion of the present invention.

Since a differential component of a pixel is used for the calculationsof the above iterative gradient method, the method is easily affected bynoises and calculation errors are increased if large gradient variationsexist in a detected block and, therefore, the LPF is applied by thepreprocessing filter 11 b to limit the high bandwidth. In the initialvector memory 11 d, motion vectors (initial vector candidates) alreadydetected in a frame immediately before the previous frame areaccumulated as initial vector candidates.

The motion vector detecting portion 11 e selects a motion vector closestto the motion vector of the detected block for an initial vector fromthe initial vector candidates accumulated in the initial vector memory11 d. The initial vector is selected by the block matching method fromthe already detected motion vectors (initial vector candidates) inneighboring blocks of the detected block. The motion vector detectingportion 11 e uses the selected initial vector as a starting point todetect a motion vector between a previous frame and a current framethrough the calculations of the gradient method.

The interpolating vector evaluating portion 11 f evaluates the motionvectors detected by the motion vector detecting portion 11 e, allocatesan optimum interpolating vector to an interpolation block between framesbased on the evaluation result, and outputs the vector to the framegenerating portion 12.

The frame generating portion 12 includes an interpolating frame memory12 a that accumulates two input frames (previous frame and currentframe), an interpolating frame generating portion 12 b that generates aninterpolating frame based on the two input frames from the interpolatingframe memory 12 a and the interpolating vector from the interpolatingvector evaluating portion 11 f, a time base conversion frame memory 12 cfor accumulating the input frames (previous frame and current frame),and a time base converting portion 12 d that inserts the interpolatingframe from the interpolating frame generating portion 12 b into theinput frames from the time base conversion frame memory 12 c to generatean output image signal (RGB signal).

The interpolating frame generating portion 12 b corresponds to aninterpolation image generating portion of the present invention and thetime base converting portion 12 d corresponds to an image interpolatingportion of the present invention.

FIG. 6 is a diagram for explaining an example of the interpolating framegenerating processing of the frame generating portion 12. Theinterpolating frame generating portion 12 b stretches an interpolatingvector V allocated to the interpolation block into the previous frameand the current frame and uses pixels located adjacent to theintersecting points with the frames to interpolate the pixels in theinterpolation block. For example, in the previous frame F₁, theluminance of a point A is calculated from three adjacent points. In thecurrent frame F₂, the luminance of a point B is calculated from threeadjacent points. In the interpolating frame F₁₂, the luminance of apoint P is interpolated using the luminance of the points A and B. Theluminance of the point P may be an average of the luminance of the pointA and the luminance of the point B, for example.

The interpolating frame F₁₂ generated as above is sent to the time baseconverting portion 12 d. The time base converting portion 12 dsandwiches the interpolating frame F₁₂ between the previous frame F₁ andthe current frame F₂ to perform processing of converting a frame rate.In this way, the FRC portion 10 may convert the input image signal (60frames/sec) into a motion-compensated output image signal (120frames/sec), which may be output to a display panel to reduce the motionblur and improve the moving image quality. Although the 60-frame/secinput image signal is converted into the 120-frame/sec (double) outputimage signal in the frame rate conversion of this description, this isobviously applicable to the case of acquiring 90-frame/sec (1.5 times)and 180-frame/sec (three times) output image signals, for example.

The image displaying device of the present invention includes the FRCportion 10 shown in FIG. 5 and the main object thereof is to make themotion compensation processing of the FRC portion 10 ineffective overthe entire screen (full screen) to prevent the image qualitydeterioration due to the FRC processing if the input image signals areimage signals likely to include a plurality of the same consecutiveimages such as a movie video and an animation video because of the 2-3pull-down processing or the 2-2 pull-down processing. Although thepresent invention is applicable to general image displaying deviceshaving the hold-type display characteristics such as liquid crystaldisplays, organic EL displays, and electrophoretic displays, arepresentative example described in the following embodiments will bethe case of applying the present invention to a liquid crystaldisplaying device using a liquid crystal display panel for a displaypanel.

In a first embodiment of the present invention, the output of the motionvector detecting portion 11 e is forced to be zero vector to make themotion compensation processing of the FRC portion 10 ineffective when apredetermined image tone mode such as, for example, the movie mode orthe game mode of a plurality of image tone modes set in the liquidcrystal displaying device is selected by a user.

FIG. 7 is a block diagram of an exemplary main configuration of a liquidcrystal displaying device according to the first embodiment of thepresent invention and the liquid crystal device includes the FRC portion10, a remote control light receiving portion 13, a controlling portion14, an image quality adjusting portion 15, a switching portion 16, azero vector portion 17, an electrode driving portion 18, and a liquidcrystal display panel 19. The switching portion 16 is disposed betweenthe motion vector detecting portion 11 e and the interpolating vectorevaluating portion 11 f within the FRC portion 10 and switches over themotion vector from the motion vector detecting portion 11 e to the zerovector portion 17 in accordance with the instruction from thecontrolling portion 14.

The remote control light receiving portion 13 receives a remote controlsignal transmitted from a remote control (remote control device) (notshown), and outputs the received signal to the controlling portion 14.The controlling portion 14 analyzes the remote control signal receivedby the remote control light receiving portion 13 and controls eachportion according to an operation instruction of the user. In this case,in the liquid crystal device of the embodiment, a “standard mode”, a“dynamic mode”, a “movie mode”, and a “game mode” are set as the imagetone modes and the user is able to instruct the device to select any oneof the image tone modes by operating a remote controller (not shown).

The controlling portion 14 analyzes the remote control signal receivedby the remote control light receiving portion 13 and when it isinstructed to select an image tone mode by the user, it outputs to theimage quality adjusting portion 15 adjustment values for luminance, grayscale, black level, color thickness, hue, contour emphasis (sharpness),etc., of the screen that are stored corresponding to the image tonemode. The image quality adjusting portion 15 applies a predeterminedimage quality adjustment to the input image signal based on the outputfrom the controlling portion 14.

For example, when a movie program or movie software is viewed, a useroperates a remote controller (not shown), selects the “movie mode” and,thereby, is able to adjust the image quality that is suitable forviewing of a movie. Similarly, when a video game is viewed, the userselects the “game mode” and, thereby, is able to adjust the imagequality that is suitable for viewing of the video game. That is, whenthe user selects the “movie mode”, a movie video image is highlyprobably input and, when the user selects the “game mode”, a game (CG)video image is highly probably input.

In the embodiment, as shown in FIG. 8, every time an image tone modeselection button provided on the remote controller (not shown) ispressed, the image tone mode is shifted in order of “standardmode”→“dynamic mode”→“movie mode”→“game mode”→“standard mode”→ . . .However, the method of selection operation of the image tone mode is notlimited to this.

The liquid crystal display panel 19 is an active-matrix liquid crystaldisplay that includes a liquid crystal layer and electrodes to apply ascan signal and a data signal to the liquid crystal layer. The electrodedriving portion 18 is a display driver to drive the scan electrodes andthe data electrodes of the liquid crystal panel 19 based on the imagesignal to which the frame rate conversion by the FRC portion 10 has beengiven. The controlling portion 14 includes a CPU for controlling theabove portions and performs control such that the motion compensationprocessing of the FRC portion 10 is made ineffective when it isdetermined that an image tone mode selected by a user is a predeterminedimage tone mode.

The drive frequency of the liquid crystal display panel 19 is a framefrequency converted by the FRC portion 10. Therefore, if an image signalinput with a frame frequency of 60 Hz is converted by the FRC portion 10into a frame frequency of 120 Hz, the drive frequency of the liquidcrystal display panel 19 is 120 Hz. However, if the frame frequencyconversion of the FRC processing is not performed and the input imagesignal is directly displayed and output, the drive frequency of theliquid crystal display panel 19 is the frame frequency of the inputimage signal.

Because a movie video image or a CG video image is highly probably inputwhen the image tone mode selected by a user is “movie mode” or “gamemode”, the controlling portion 14 switches the switching portion 16 tothe zero-vector 17 to forcibly replace the motion vector detected by themotion vector detecting portion 11 e with the zero-vector. When theimage tone mode selected by the user is a mode other than “movie mode”and “game mode” (that is “standard mode” or “dynamic mode” in theembodiment), the switching portion 16 is switched to the motion vectordetecting portion 11 e to input the motion vector detected by the motionvector detecting portion 11 e to the interpolating vector evaluatingportion 11 f.

Therefore, the moving image quality may be improved by themotion-compensated FRC processing at the time of the normal moving imagedisplay and, when a moving image such as movie or game (CG) likely toinclude a plurality of the same consecutive images is input, thedetection errors, the motion compensation errors, etc., of the motionvector due to the discontinuity of the image movement are eliminated andthe image quality may effectively be prevented from deteriorating due tothe motion-compensated FRC processing by making the motion compensationprocessing ineffective with the motion vector set to zero-vector.

In a second embodiment of the present invention, when a predeterminedimage tone mode such as, for example, movie mode or game mode of aplurality of image tone modes set in the liquid crystal displayingdevice is selected by a user, the interpolating vector from theinterpolating vector evaluating portion 11 f is set to zero-vector tomake the motion compensation processing of the FRC portion 10ineffective so that no interpolation can occur between pixels located atdifferent positions.

FIG. 9 is a block diagram of an exemplary main configuration of a liquidcrystal displaying device according to the second embodiment of thepresent invention and the liquid crystal displaying device includes theFRC portion 10, the remote control light receiving portion 13, thecontrolling portion 14, the image quality adjusting portion 15, theswitching portion 16, the zero-vector portion 17, the electrode drivingportion 18, and the liquid crystal display panel 19. The switchingportion 16 is disposed between the interpolating vector evaluatingportion 11 f and the interpolating frame generating portion 12 b withinthe FRC portion 10 and switches the interpolating vector from theinterpolating vector evaluating portion 11 f to the zero-vector 17 inaccordance with the instruction from the controlling portion 14.

Because a movie video image or a CG video image is highly probably inputwhen the image tone mode selected by a user is “movie mode” or “gamemode”, the controlling portion 14 switches the switching portion 16 tothe zero-vector 17 to set the interpolating vector allocated by theinterpolating vector evaluating portion 11 f to zero-vector. When theimage tone mode selected by the user is “standard mode” or “dynamicmode”, the switching portion 16 is switched to the interpolating vectorevaluating portion 11 f to input the interpolating vector allocated bythe interpolating vector evaluating portion 11 f to the interpolatingframe generating portion 12 b.

When the moving image such as movie or game (CG) likely to include aplurality of the same consecutive images is input, the detection errors,the motion compensation errors, etc., of the motion vector due to thediscontinuity of the image movement are eliminated in the same was asdescribed in the first embodiment and the image quality may effectivelybe prevented from deteriorating due to the motion-compensated FRCprocessing by making the motion compensation processing ineffective withthe interpolating vector forcibly set to zero-vector.

In a third embodiment of the present invention, a path is provided tobypass the FRC portion 10 and, when a predetermined image tone mode suchas, for example, movie mode or game mode of the plurality of image tonemodes set in the liquid crystal displaying device is selected by a user,the input image signal is input to the bypass to change the drivefrequency of the liquid crystal display panel 19 in conformity with theframe frequency of the input image signal. When a predetermined imagetone mode determined in advance is selected, the switching is performedsuch that the input image signal is directly output and displayed on theliquid crystal display panel 19 without performing the frame rateconversion.

FIG. 10 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to the third embodiment ofthe present invention and the liquid crystal displaying device includesthe FRC portion 10, the remote control light receiving portion 13, thecontrolling portion 14, the image quality adjusting portion 15, theswitching portion 16, the electrode driving portion 18, the liquidcrystal display panel 19, and a path 20 for bypassing the FRC portion10. The switching portion 16 is disposed on the previous stage of theFRC portion 10 and switches the input image signal to input whether tothe FRC portion 10 or to the path 20 in accordance with the instructionfrom the controlling portion 14.

When the image tone mode selected by the user is “movie mode” or “gamemode”, the controlling portion 14 shifts the switching portion 16 to thepath 20 to bypass the FRC portion 10. When the image tone mode selectedby the user is “standard mode” or “dynamic mode”, the switching portion16 is shifted to the FRC portion 10 to perform the FRC processing(motion-compensated frame interpolation processing) for the input imagesignal. The switching portion 16 may be disposed on the subsequent stageof the FRC portion 10 such that the output signal of the FRC portion 10and the output signal of the path 20 are switched over to output to theliquid crystal display panel 19.

In this embodiment, the controlling portion 14 may change the drivefrequency of the liquid crystal display panel 19, and when “movie mode”or “game mode” is selected, the input image signal is input to the path20 to change the drive frequency of the liquid crystal display panel 19in conformity with the frame frequency of the input image signal.

FIG. 11 is a diagram of a relationship between input data and outputdata according to the third embodiment of the present invention. FIG.11(A) depicts the input data to the path 20 and FIG. 11(B) depicts theoutput data from the path 20. As shown in FIG. 11(A), if the input imagesignal (input data) is input to the path 20 with a frame frequency of 60Hz, the display time per frame is about 16.7 ms. The controlling portion15 controls the electrode driving portion 18, which is the displaydriver, to change the drive frequency of the liquid crystal displaypanel 19 from 120 Hz to 60 Hz and causes the input data to be outputfrom the path 20 at 60 Hz without performing the frame rate conversionas shown in FIG. 11(B).

Since the liquid crystal display panel 19 displays the frame output fromthe path 20 without the frame rate conversion at the drive frequency of60 Hz, the display time per frame is still about 16.7 ms.

Therefore, the moving image quality may be improved by themotion-compensated FRC processing at the time of the normal moving imagedisplay and, when the moving image such as movie or game (CG) likely toinclude a plurality of the same consecutive images is input, thedetection errors, the motion compensation errors, etc., of the motionvector due to the discontinuity of the image movement are eliminated andthe image quality may effectively be prevented from deteriorating due tothe motion-compensated FRC processing by prohibiting the frame rateconversion itself with the FRC processing bypassed.

In a fourth embodiment of the present invention, a path is provided tobypass the FRC portion 10 and, when a predetermined image tone mode suchas, for example, movie mode or game mode of the plurality of image tonemodes set in the liquid crystal displaying device is selected by a user,the input image signal is input to the bypass to accumulate the inputimage signal in a memory on the path and the frame rate is converted byrapidly and repeatedly reading the image signal of the same frame fromthe memory more than once. When a predetermined image tone mode isselected, the switching is performed such that the input image signal israpidly and sequentially output to convert the frame rate and is outputand displayed on the liquid crystal display panel 19 without performingthe motion-compensated frame rate conversion.

FIG. 12 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to the fourth embodiment ofthe present invention and the liquid crystal displaying device includesthe FRC portion 10, the remote control light receiving portion 13, thecontrolling portion 14, the image quality adjusting portion 15, theswitching portion 16, the electrode driving portion 18, the liquidcrystal display panel 19, the path 20 for bypassing the FRC portion 10,and a memory 21 on the path 20. The switching portion 16 is disposed onthe previous stage of the FRC portion 10 and switches the input imagesignal to input whether to the FRC portion 10 or to the path 20 inaccordance with the instruction from the controlling portion 14.

When the image tone mode selected by a user is “movie mode” or “gamemode”, the controlling portion 14 shifts the switching portion 16 to thepath 20 to bypass the FRC portion 10 and to accumulate the input imagesignal in the memory 21. The frame insert processing is subsequentlyperformed by repeatedly reading the same frame from the memory 21 morethan once. When the image tone mode selected by the user is “standardmode” or “dynamic mode”, the switching portion 16 is switched to the FRCportion 10 to perform the FRC processing (motion-compensated frameinterpolation processing) for the input image signal. The switchingportion 16 may be disposed on the subsequent stage of the FRC portion 10such that the output signal of the FRC portion 10 and the output signalof the memory 21 are switched over to output to the liquid crystaldisplay panel 19.

In this embodiment, the drive frequency of the liquid crystal displaypanel 19 is not changed and is maintained at 120 Hz. When “movie mode”or “game mode” is selected, the controlling portion 14 and the memory 21comprise a portion for converting the number of frames of the inputimage signal by inserting an image signal of the previous or subsequentframe between the frames of the input image signal. The frame rate (thenumber of frames) of the display image signal input to the electrodedriving portion 18 is always the same.

FIG. 13 is a view of a relationship between input data and output dataaccording to the fourth embodiment of the present invention. FIG. 13(A)shows the input data to the path 20 and FIG. 13(B) shows the output datafrom the path 20. As shown in FIG. 13(A), if the input image signal(input data) is input to the path 20 with a frame frequency of 60 Hz,the display time per frame is about 16.7 ms. The input data aretemporarily accumulated in the memory 21, and an image signal of theframe (in FIG. 13, frame A) is output which is repeatedly read from thememory 21 at double speed as shown in FIG. 13(B).

The liquid crystal display panel 19 displays the output data into whichthe image signal of the same frame has been inserted, at the drivefrequency of 120 Hz. Since the number of frames is converted byrepeatedly reading the same frame twice, the display time per frame isabout 8.3 ms in this case.

When the moving image such as movie or game (CG) likely to include aplurality of the same consecutive images is input, the detection errors,the motion compensation errors, etc., of the motion vector due to thediscontinuity of images are eliminated and the image quality mayeffectively be prevented from deteriorating due to themotion-compensated FRC processing by not performing the interpolationprocessing through motion compensation for the input image signal. Sincethe frame rate is converted by repeatedly reading the same frame in thiscase, the drive frequency of the liquid crystal display panel 19 doesnot need to be changed.

In a fifth embodiment of the present invention, a path is provided tobypass the FRC portion 10 and, when a predetermined image tone mode suchas, for example, movie mode or game mode of the plurality of image tonemodes set in the liquid crystal displaying device is selected by a user,the input image signal is input to the bypass and the input image signalis input to a linear interpolation processing portion on the path tointerpolate an image signal to which the linear interpolation has beenperformed. When a predetermined image tone mode is selected, theswitching is performed such that the frame rate is converted byperforming the linear interpolation processing rather than theinterpolation processing through motion compensation.

FIG. 14 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to the fifth embodiment ofthe present invention and the liquid crystal displaying device includesthe FRC portion 10, the remote control light receiving portion 13, thecontrolling portion 14, the image quality adjusting portion 15, theswitching portion 16, the electrode driving portion 18, the liquidcrystal display panel 19, the path 20 for bypassing the FRC portion 10,and a linear interpolation processing portion 22 on the path 20. Theswitching portion 16 is disposed on the previous stage of the FRCportion 10 and switches the input image signal to input whether to theFRC portion 10 or to the path 20 in accordance with the instruction fromthe controlling portion 14.

When the image tone mode selected by a user is “movie mode” or “gamemode”, the controlling portion 14 shifts the switching portion 16 to thepath 20 to bypass the FRC portion 10 and the input image signal is inputto the linear interpolation processing portion 22. The linearinterpolation processing portion 22 inserts an interpolating frame towhich the linear interpolation processing has been given between frames.When the image tone mode selected by the user is “standard mode” or“dynamic mode”, the switching portion 16 is switched to the FRC portion10 to perform the FRC processing (motion-compensated frame interpolationprocessing) for the input image signal. The switching portion 16 may bedisposed on the subsequent stage of the FRC portion 10 such that theoutput signal of the FRC portion 10 and the output signal of the linearinterpolation processing portion 22 are switched over to output to theliquid crystal display panel 19.

In this embodiment, the drive frequency of the liquid crystal displaypanel 19 is not changed and is maintained at 120 Hz. The frame rate (thenumber of frames) of the display image signal input to the electrodedriving portion 18 is always the same. When “movie mode” or “game mode”is selected, the linear interpolation processing portion 22 comprises aportion for converting the number of frames of the input image signal byinterpolating an image signal to which the linear interpolationprocessing has been given between the frames of the input image signal.In the linear interpolation processing, as described in the abovedocument (Yamauchi Tatsuro, “TV Standards Conversion”, Journal of theInstitute of Television Engineers of Japan, Vol. 45, No. 12, pp.1534-1543 (1991)), an interpolating frame is acquired through linearinterpolation using a frame interpolation ratio α from the signal of theprevious frame and the signal of the current frame.

FIG. 15 is a view of a relationship between input data and output dataaccording to the fifth embodiment of the present invention. FIG. 15(A)shows the input data to the path 20 and FIG. 15(B) shows the output datafrom the path 20. As shown in FIG. 15(A), if the input image signal(input data) is input to the path 20 with a frame frequency of 60 Hz,the display time per frame is about 16.7 ms. The input data are input tothe linear interpolation processing portion 22, and the image signal towhich the linear interpolation processing has been given (in FIG. 15,frame A+B) is interpolated and output between the frames (in this case,between frames A and B) as shown in FIG. 15(B).

The liquid crystal display panel 19 displays the output data into whichthe image signal to which the linear interpolation processing has beengiven, is interpolated at the drive frequency of 120 Hz. Since thenumber of frames is converted by interpolating the image signal to whichthe linear interpolation processing has been given, the display time perframe is about 8.3 ms in this case.

When the moving image such as movie or game (CG) likely to include aplurality of the same consecutive images is input, the detection errors,the motion compensation errors, etc., of the motion vector due to thediscontinuity of images are eliminated and the image quality mayeffectively be prevented from deteriorating due to themotion-compensated FRC processing by not performing the interpolationprocessing through motion compensation for the input image signal. Sincethe frame rate is converted by interpolating the image signal to whichthe linear interpolation processing has been given in this case, thedrive frequency of the liquid crystal display panel 19 does not need tobe changed.

In a sixth embodiment of the present invention, a path is provided tobypass the FRC portion 10 and, when a predetermined image tone mode suchas, for example, movie mode or game mode of the plurality of image tonemodes set in the liquid crystal displaying device is selected by a user,the input image signal is input to the bypass and the input image signalis input to a black-level signal insertion processing portion on thepath to insert a predetermined monochromatic image signal such as ablack-level signal. When a predetermined image tone mode is selected,the switching is performed such that the frame rate is converted byperforming the monochromatic image insertion processing rather than theinterpolation processing through motion compensation.

FIG. 16 is a block diagram of an exemplary main configuration of aliquid crystal displaying device according to the sixth embodiment ofthe present invention and the liquid crystal displaying device includesthe FRC portion 10, the remote control light receiving portion 13, thecontrolling portion 14, the image quality adjusting portion 15, theswitching portion 16, the electrode driving portion 18, the liquidcrystal display panel 19, the path 20 for bypassing the FRC portion 10,and a black-level signal insertion processing portion 23 on the path 20.The switching portion 16 is disposed on the previous stage of the FRCportion 10 and switches the input image signal to input whether to theFRC portion 10 or to the path 20 in accordance with the instruction fromthe controlling portion 14.

When the image tone mode selected by a user is “movie mode” or “gamemode”, the controlling portion 14 shifts the switching portion 16 to thepath 20 to bypass the FRC portion 10 and the input image signal is inputto the black-level signal insertion processing portion 23. Theblack-level signal insertion processing portion 23 performs the timescale compression (frame rate conversion) for the input image signal,for example, with the use of a memory to insert the predeterminedmonochromatic image signal such as a black-level signal between theinput frames. When the image tone mode selected by the user is “standardmode” or “dynamic mode”, the switching portion 16 is shifted to the FRCportion 10 to perform the FRC processing (motion-compensated frameinterpolation processing) for the input image signal. The switchingportion 16 may be disposed on the subsequent stage of the FRC portion 10such that the output signal of the FRC portion 10 and the output signalof the black-level signal insertion processing portion 23 are switchedover to output to the liquid crystal display panel 19.

In this embodiment, the drive frequency of the liquid crystal displaypanel 19 is not changed and is maintained at 120 Hz. The frame rate (thenumber of frames) of the display image signal input to the electrodedriving portion 18 is always the same. When “movie mode” or “game mode”is selected, the black-level signal insertion processing portion 23comprises a portion for converting the number of frames of the inputimage signal by inserting the predetermined monochromatic image signalsuch as a black-level signal between the frames of the input imagesignal. Another embodiment of the black-level signal insertionprocessing may be configured such that the electrode driving portion 18applies a voltage for writing black to the liquid crystal display panel19 for a predetermined period (in the case of this example, 1/120second).

FIG. 17 is a view of a relationship between input data and output dataaccording to the sixth embodiment of the present invention. FIG. 17(A)shows the input data to the path 20 and FIG. 17(B) shows the output datafrom the path 20. As shown in FIG. 17(A), if the input image signal(input data) is input to the path 20 with a frame frequency of 60 Hz,the display time per frame is about 16.7 ms. The input data are input tothe black-level signal insertion processing portion 23, and ablack-level signal (in FIG. 17, black-colored frame) is inserted andoutput between the frames (in this case, between the frames A and B) asshown in FIG. 17(B).

Although the image quality deterioration due to the motion blur isimproved and the image quality deterioration due to the motioncompensation error is not generated by inserting the black image signalbetween the frames of the input image signal in this way, the emissionluminance must be increased in a backlight (not shown) disposed on thebackside of the liquid crystal display panel 19 to compensate thereduction of the display luminance due to the shortening of the imagedisplay period.

The liquid crystal display panel 19 displays the output data, into whichthe black-level signal has been inserted, at the drive frequency of 120Hz. Since the number of frames is converted by inserting the black-levelsignal, the display time per frame is about 8.3 ms in this case.

When a moving image such as movie or game (CG) likely to include aplurality of the same consecutive images is input, the detection errors,the motion compensation errors, etc., of the motion vector due to thediscontinuity of images are eliminated and the image quality mayeffectively be prevented from deteriorating due to themotion-compensated FRC processing by not performing the interpolationprocessing through motion compensation for the input image signal. Sincethe frame rate is converted by inserting the monochromatic image signalin this case, the drive frequency of the liquid crystal display panel 19does not need to be changed. The moving image quality improving effectmay also be maintained in this case.

Other than the above embodiment, when a predetermined image tone modesuch as movie mode or game mode is selected, the image quality may beprevented from deteriorating due to the motion-compensated FRCprocessing and the moving image quality improving effect may bemaintained at the same time by dividing the original image of the inputframe into a plurality of frame images at a predetermined luminanceratio for the frame rate conversion.

In a seventh embodiment of the present invention, when a predeterminedimage tone mode such as, for example, movie mode or game mode of theplurality of image tone modes set in the liquid crystal displayingdevice is selected by a user, the compensation intensity of the motioncompensation processing may be varied in the interpolating framegenerating portion. Specifically, the weighted addition rate may bevaried when the pull-down converted image signal is input by providingthe interpolating frame generating portion that performs weightedaddition of the image signal to which the motion compensation processinghas been given and the image signal to which the linear interpolationprocessing has been given at a predetermined rate to generate aninterpolating frame.

FIG. 18 is a block diagram of an exemplary main configuration of the FRCportion 10 according to the seventh embodiment of the present invention,and the frame generating portion 12 of the FRC portion 10 includes theinterpolating frame memory 12 a, the interpolating frame generatingportion 12 b, and a compensation intensity varying portion 12 e that mayvary the compensation intensity of the motion compensation processing inthe FRC portion 10. In FIG. 18, V denotes an interpolating vector; αdenotes a frame interpolation ratio; and β denotes interpolationintensity (weighted addition rate).

Generally, for example, the frame interpolation through the linearinterpolation between two frames and the frame interpolation usingmotion vectors (motion compensated interpolation) are known as methodsof the frame interpolation processing. In the former case, aninterpolating frame is acquired by the linear interpolation from thesignal of the previous frame and the signal of the current frame at aframe interpolation ratio α. Therefore, using this linear interpolationmay prevent the image quality deterioration due to the motioncompensation errors in the FRC processing.

On the other hand, to acquire an interpolating frame from the previousframe and the current frame in the latter case, the interpolating vectorV is detected from the motion vectors between the previous frame imageand the current frame image, and the interpolating frame is acquiredfrom the weighted addition of a signal of the previous frame imageshifted by a degree of αV obtained by dividing the value (interpolatingvector V) by the frame interpolation ratio α and a signal of the currentframe image shifted by (1−α)V. Although good image quality may beacquired without deteriorating the resolution since a moving imageitself is captured and compensated by using this motion-compensatedinterpolation, the image quality may be deteriorated in the pulled-downvideo due to this processing.

Therefore, in this embodiment, the compensation intensity varyingportion 12 e is disposed in the frame generating portion 12. When theimage tone mode selected by a user is “movie mode” or “game mode”, thecompensation intensity varying portion 12 e varies the weighted additionrate β. The weighted addition rate β is a rate for performing theweighted addition of the image signal to which the motion compensationprocessing has been given and the image signal to which the linearinterpolation processing has been given. The interpolating framegenerating portion 12 b of this embodiment performs the weightedaddition of the linear interpolation and the motion-compensatedinterpolation in accordance with the weighted addition rate β togenerate the interpolating frame.

For example, when the image tone mode selected by the user is “moviemode” or “game mode”, the compensation intensity varying portion 12 esets the weighted addition rate β=0 and defines the image signal towhich the linear interpolation processing has been given as theinterpolating frame to prevent the image deterioration. On the otherhand, when the image tone mode selected by the user is “standard mode”or “dynamic mode”, the weighted addition rate β=1 is set to define theimage signal to which the motion compensation processing has been givenas the interpolating frame to achieve better image quality for themoving image.

Since the weighted addition rate β may arbitrarily and variably be set,the rate may be set to a substantially intermediate value between zeroand one. This enables to control the deterioration of the image qualityand to perform the motion compensation in the interpolating frame imageat the same time, and this may appropriately improve both the imagequality deterioration due to the motion blur and the image qualitydeterioration due to the motion compensation errors.

Since the compensation intensity may be varied (weakened) in the motioncompensation processing in the FRC when the moving image such as movieor game (CG) likely to include a plurality of the same consecutiveimages is input, the image quality deterioration due to themotion-compensated FRC process may effectively be controlled by reducingthe effects of the detection errors, the motion compensation errors,etc., of the motion vector due to the discontinuity of images.

FIG. 19 is a flowchart for explaining an example of an image displayingmethod by the image displaying device of the present invention. Anexample of the image displaying method in the first embodiment will bedescribed. First, the image displaying device determines whether theimage tone mode selected by a user is “movie mode” based on a remotecontrol signal received (step S1), and if it is determined that theimage tone mode is “movie mode” (in the case of YES), the motion vectoror the interpolating vector is set to zero-vector to make the motioncompensation processing of the FRC portion 10 ineffective (step S2). Ifit is determined at step S1 that the image tone mode selected by theuser is not “movie mode” (in the case of NO), it is determined whetherthe image tone mode selected by the user is “game mode” (step S3).

If it is determined at step S3 that the image tone mode is “game mode”(in the case of YES), the motion vector or the interpolating vector isset to zero-vector to make the motion compensation processing of the FRCportion 10 ineffective (step S2), and if it is determined that the imagetone mode is not “game mode” (in the case of NO), the motioncompensation processing of the FRC portion 10 is executed as usual (stepS4). The image signal with the frame frequency converted in this way isdisplayed and output from the liquid crystal display panel 19 (step S5).

FIG. 20 is a flowchart for explaining another example of the imagedisplaying method by the image displaying device of the presentinvention. An example of the image displaying method in the second tosixth embodiments will be described. First, the image displaying devicedetermines whether the image tone mode selected by a user is “moviemode” based on a remote control signal received (step S11), and if it isdetermined that the image tone mode is “movie mode” (in the case ofYES), the motion-compensated frame interpolation processing of the FRCportion 10 is bypassed and the input image signal is input to the otherpath 20 (step S12).

On the bypassing path 20, the image signal is output after the framerate is converted by executing any one of the inter-frame interpolationof the image signal to which the linear interpolation processing hasbeen given, the inter-frame interpolation of the image signal of thesame frame, and the inter-frame interpolation of the predeterminedmonochromatic image signal such as a black-level signal, or the inputimage signal is directly output to execute processing such as changingthe drive frequency of the liquid crystal display panel 19.

If it is determined at step S11 that the image tone mode selected by theuser is not “movie mode” (in the case of NO), it is determined whetherthe image tone mode selected by the user is “game mode” (step S13). Ifit is determined at step S13 that the image tone mode is “game mode” (inthe case of YES), the motion-compensated frame interpolation processingof the FRC portion 10 is bypassed and the input image signal is input tothe other path 20 (step S12), and the image signal is output after theframe rate is converted by executing any one of the inter-frameinterpolation of the image signal to which the linear interpolationprocessing has been given, the inter-frame interpolation of the imagesignal of the same frame, and the inter-frame interpolation of thepredetermined monochromatic image signal such as a black-level signal,or the input image signal is directly output to execute processing suchas changing the drive frequency of the liquid crystal display panel 19.If it is determined at step S13 that the image tone mode is not “gamemode” (in the case of NO), the image signal is output that is given themotion-compensated interpolation processing of the FRC portion 10 (stepS14). Finally, the image is displayed and output from the liquid crystaldisplay panel 19 (step S15).

FIG. 21 is a flowchart for explaining another example of the imagedisplaying method by the image displaying device of the presentinvention. An example of the image displaying method in the seventhembodiment will be described. First, the image displaying devicedetermines whether the image tone mode selected by a user is “moviemode” based on a remote control signal received (step S21), and if it isdetermined that the image tone mode is “movie mode” (in the case ofYES), the compensation intensity is varied (weakened) in the motioncompensation processing of the FRC portion 10 (step S22). If it isdetermined at step S21 that the image tone mode selected by the user isnot “movie mode” (in the case of NO), it is determined whether the imagetone mode selected by the user is “game mode” (step S23).

If it is determined at step S23 that the image tone mode is “game mode”(in the case of YES), the compensation intensity is varied (weakened) inthe motion compensation processing of the FRC portion 10 (step S22). Ifit is determined at step S23 that that the image tone mode is not “gamemode” (in the case of NO), the compensation intensity is increased asusual in the motion compensation processing of the FRC portion 10 (stepS24). The image signal with the frame frequency converted in this way isdisplayed and output from the liquid crystal display panel 19 (stepS25).

As above, according to the present invention, when an image tone modesuch as movie mode or game mode is selected, a moving image signallikely to include a plurality of the same consecutive images is highlyprobably input and, since displaying and outputting are performed bymaking the motion compensation processing in the frame rate converting(FRC) portion ineffective, the image quality may effectively beprevented from deteriorating due to the motion compensation errors. Itis needless to say that the image signal is not limited to thetelevision image signal and may be an image signal reproduced from anexternal medium.

In the above embodiment, the image displaying device has been describedthat has the four image tone modes set therein and that controls themotion compensation processing of the frame rate converting (FRC)portion when “movie mode” or “game mode” of the four modes is selectedby a user. However, the image tone modes set in the image displayingdevice may be those other than the above modes and, in the case where,for example, a PC (Personal Computer) mode suitable for a PC video imageand an animation mode suitable for an animation video image areprovided, when the PC mode or the animation mode is selected, the imagedisplaying device may control the motion compensation processing by theframe rate converting (FRC) portion.

Although the exemplary embodiments related to the image displayingdevice and method of the present invention have been described as above,the above description will facilitate understanding of an imagedisplaying program operable to drive a computer to execute the imagedisplaying method as a program and a program recording medium, which isa computer-readable recording medium having the image displaying programrecorded thereon.

1-27. (canceled)
 28. An image displaying device having a rate convertingportion that converts the number of frames or fields of an input imagesignal by interpolating an interpolation image signal between frames orfields of the input image signal, wherein a mode setting portion for auser to select and set an image tone mode to set and adjust the imagequality of a display image from a plurality of image tone modes preparedin advance, wherein the rate converting portion comprises aninterpolation image generating portion that generates an interpolationimage signal by giving the motion compensation processing to the inputimage signal based on motion vector information between the frames orfields of the input image signal, and the interpolation of the imagesignal generated by giving the motion compensation processing is notexecuted when the image tone mode set by the mode setting portion is apredetermined image tone mode set in advance as an image tone modesuitable for displaying a video image including a moving image likely toinclude the same consecutive images in a plurality of frames or fields.29. The image displaying device as defined in claim 28, wherein the rateconverting portion interpolates an image signal generated by making themotion compensation processing in the interpolation image generatingportion ineffective between the frames or fields of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.
 30. The image displaying device asdefined in claim 29, wherein the interpolation image generating portioncomprises: a motion vector detecting portion that detects the motionvector information between consecutive frames or fields included in theinput image signal; and an interpolating vector allocating portion thatallocates an interpolating vector between the frames or fields based onthe detected motion vector information.
 31. The image displaying deviceas defined in claim 30, wherein the interpolation image generatingportion makes the motion compensation processing ineffective by settingthe motion vector detected by the motion vector detecting portion tozero-vector when the image tone mode set by the mode setting portion isthe predetermined image tone mode.
 32. The image displaying device asdefined in claim 30, wherein the interpolation image generating portionmakes the motion compensation processing ineffective by setting theinterpolating vector allocated by the interpolating vector allocatingportion to zero-vector when the image tone mode set by the mode settingportion is the predetermined image tone mode.
 33. The image displayingdevice as defined in claim 28, which does not insert the interpolationimage signal generated by giving the motion compensation processingbetween the frames or fields of the input image signal and does notconvert the number of frames or fields of the input image signal whenthe image tone mode set by the mode setting portion is the predeterminedimage tone mode.
 34. The image displaying device as defined in claim 33,wherein a driving frequency of a display panel displaying the imagesignal is variable, and the image displaying device comprises a portionfor varying the driving frequency of the display panel from the framefrequency or the field frequency converted by the rate convertingportion to the frame frequency or the field frequency of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.
 35. The image displaying device asdefined in claim 28, wherein the rate converting portion converts thenumber of frames or fields of the input image signal by inserting animage signal to which the motion compensation processing has not beengiven between the frames or fields of the input image signal when theimage tone mode set by the mode setting portion is the predeterminedimage tone mode.
 36. The image displaying device as defined in claim 35,wherein the rate converting portion converts the number of frames orfields of the input image signal by inserting an image signal of theframes or fields between frames or fields of the input image signal whenthe image tone mode set by the mode setting portion is the predeterminedimage tone mode.
 37. The image displaying device as defined in claim 35,wherein the rate converting portion converts the number of frames orfields of the input image signal by interpolating an image signal formedby giving a linear interpolation processing to an image signal of theframes or fields between frames or fields of the input image signal whenthe image tone mode set by the mode setting portion is the predeterminedimage tone mode.
 38. The image displaying device as defined in claim 34,wherein the rate converting portion converts the number of frames orfields of the input image signal by inserting a predeterminedmonochromatic image signal between frames or fields of the input imagesignal when the image tone mode set by the mode setting portion is thepredetermined image tone mode.
 39. The image displaying device asdefined in claim 28, wherein the predetermined image tone mode is moviemode.
 40. The image displaying device as defined in claim 28, whereinthe predetermined image tone mode is game mode.
 41. An image displayingdevice as defined in claim 28, wherein the rate converting portionconverts a frame frequency or field frequency of the input image signalinto integral multiples of each.
 42. An image displaying method having arate converting process for converting the number of frames or fields ofan input image signal by interpolating an interpolation image signalbetween frames or fields of the input image signal, wherein the processin which a user is caused to select and set an image tone mode to setand adjust the image quality of a display image from a plurality ofimage tone modes prepared in advance is included, and the rateconverting process has an interpolation image generating process forgenerating an interpolation image signal by giving the motioncompensation processing to the input image signal based on motion vectorinformation between frames or fields of the input image signal, and theinterpolation of the image signal generated by giving the motioncompensation processing is not executed when the image tone mode set bythe user is a predetermined image tone mode set in advance as an imagetone mode suitable for displaying a video image including a moving imagelikely to include the same consecutive images in a plurality of framesor fields.
 43. The image displaying method as defined in claim 42,wherein in the rate converting process, the image signal generated bymaking the motion compensation processing in the interpolation imagegenerating portion ineffective is interpolated between the frames orfields of the input image signal when the image tone mode set by themode setting portion is the predetermined image tone mode.
 44. The imagedisplaying method as defined in claim 42, wherein the interpolationimage signal generated by giving the motion compensation processing isnot inserted between the frames or fields of the input image signal andthe number of frames or fields of the input image signal is notconverted when the image tone mode set by the user is the predeterminedimage tone mode.
 45. The image displaying method as defined in claim 42,wherein in the rate converting process, the number of frames or fieldsof the input image signal is converted by inserting an image signal ofthe frames or fields between frames or fields of the input image signalwhen the image tone mode set by the user is the predetermined image tonemode.
 46. The image displaying method as defined in claim 42, wherein inthe rate converting process, the number of frames or fields of the inputimage signal is converted by interpolating an image signal formed bygiving a linear interpolation processing to the image signal of theframes or fields between frames or fields of the input image signal whenthe image tone mode set by the user is the predetermined image tonemode.
 47. The image displaying method as defined in claim 42, wherein inthe rate converting process, the number of frames or fields of the inputimage signal is converted by inserting a predetermined monochromaticimage signal between the frames or fields of the input image signal whenthe image tone mole set by the user is the predetermined image tonemode.
 48. An image displaying device having a rate converting portionthat converts the number of frames or fields of an input image signal byinterpolating an interpolation image signal between frames or fields ofthe input image signal, wherein a mode setting portion for a user toselect and set an image tone mode to set and adjust the image quality ofa display image from a plurality of image tone modes prepared inadvance, wherein the rate converting portion comprises an interpolationimage generating portion that generates an interpolation image signal bygiving the motion compensation processing to the input image signalbased on motion vector information between the frames or fields of theinput image signal, and interpolates an interpolation image signalgenerated by reducing the strength of the compensation of the motioncompensation processing between frames or fields of the input imagesignal when the image tone mode set by the mode setting portion is apredetermined image tone mode suitable for displaying a video imageincluding a moving image likely to include the same consecutive imagesin a plurality of frames or fields.
 49. The image displaying device asdefined in claim 48, wherein the interpolation image generating portiongenerates an interpolation image signal by performing weighted additionof the image signal to which the motion compensation processing has beengiven and an image signal to winch the motion compensation processinghas not been given at a predetermined rate, and the rate of the weightedaddition is varied when the genre determined by the determining portionis the predetermined genre.
 50. The image displaying device as definedin claim 49, wherein the interpolation image generating portion definesthe image signal to which the motion compensation processing has notbeen given as the interpolation image signal when the image tone modeset by the mode setting portion is the predetermined image tone mode,and defines the image signal to which the motion compensation processinghas been given as the interpolation image signal when the image tonemode set by the mode setting portion is not the predetermined image tonemode.
 51. The image displaying device as defined in claim 49, whereinthe interpolation image generating portion uses an image signal to whicha linear interpolation processing has been given between the frames orfields of the input image signal as the image signal to which the motioncompensation processing has not been given.
 52. The image displayingdevice as defined in claim 48, wherein the predetermined image tone modeis movie mode.
 53. The image displaying device as defined in claim 48,wherein the predetermined image tone mode is game mode.
 54. An imagedisplaying method having a rate converting process for converting thenumber of frames or fields of an input image signal by interpolating aninterpolation image signal between frames or fields of the input imagesignal, wherein the process in which a user is caused to select and setan image tone mode to set and adjust the image quality of a displayimage from a plurality of image tone modes prepared in advance isincluded, and the rate converting process has an interpolation imagegenerating process for generating an interpolation image signal bygiving the motion compensation processing to the input image signalbased on motion vector information between frames or fields of the inputimage signal, and the interpolation image signal generated by reducingthe strength of the compensation of the motion compensation processingis interpolated between the frames or fields of the input image signalwhen the image tone mode set by the user is a predetermined image tonemode set in advance as an image tone mode suitable for displaying avideo image including a moving image likely to include the sameconsecutive images in a plurality of frames or fields.